PRODUCTION OF CONTINUOUSLY CAST SLAB HAVING EXCELLENT INTERNAL QUALITY

摘要

PURPOSE: To stick the central cavity by pressing and to obtain a continuously cast slab having excellent internal quality without internal crack by continuously casting a low carbon molten steel and executing rolling reduction in a specific condition of the rolling reduction during the unsolidified condition in the center part of the cast slab at the end period of the solidification. ;CONSTITUTION: Molten steel having $0.18C is continuously cast and one time of the rolling reduction is executed at 2-5% rolling reduction ratio to the part having 90-98% solid phase ratio fS in the center part of the cast slab at the end period of the solidification with rolling reduction rolls having the diameter of 2-5 times of the cast slab thickness. In the case of being 90% the solid phase ratio fS, the internal crack is developed because the solidified shell is weak, and in the case of being 98%, the center cavity is not stuck by pressing because the rolling reduction is not affected to the center. Further, in the case of being 5% the rolling reduction ratio, negative segregation is developed, and in the case of being 2%, the center cavity is not stuck by pressing. Further, in the case of being ≥2 the ratio of the roll diameter and the cast slab thickness, the cross sectional area compressive rate and the deformed rate are made to be large and contribute to the sticking of the central cavity by pressing, but in the case of being ≥5 this ratio, the bulging in the cast slab between the rolling reduction rolls is developed.;COPYRIGHT: (C)1995,JPO